The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations. As the fast advance of the GPS technology, GPS receivers have been miniaturized to just a few integrated circuits and so are becoming very economical and compact, that makes the technology accessible to virtually everyone and almost anywhere. Nowadays, GPS technology has matured into a resource that goes far beyond being used in an navigation system stationed in an automobile, but is finding its way into handheld satellite navigation devices, such as a portable GPS satellite unit, a personal digital assistant (PDA) with built-in GPS module, or a PDA connected externally to a GPS module, etc. However, all those handheld satellite navigation devices currently available are only PDAs with additional GPS function, that are achieved by connecting a GPS module to a PDA through either a RS-232 transmission line or an universal serial bus (USB). The aforesaid method of connecting GPS modules to PDAs not only can not integrate functions of the two devices, but also can not make good use of the software/hardware resources of the two.
As a conventional automobile navigation system disclosed in TW Pat. No. 00432833, the navigation data received by a satellite navigation system stationed in a vehicle is transmitted to a portable device so that a user carrying the portable device can use the navigation data stored therein for guidance while leaving the automobile. However, as the aforesaid data transmission is accomplished either by a wired means or a wireless means, it is obvious that the means of connecting the automobile satellite navigation system and the portable device not only can not integrate functions of the two devices, but also can not make good use of the software/hardware resources of the portable device.
Therefore, it is in need of an automobile navigation system with portable telematics device, which utilizes a specific control data bus capable of supporting multiple data transmission protocols to connect and integrate a portable telematics device with the automobile navigation system and so not only the cost of the automobile navigation system is reduced, but also the software/hardware resources of the portable device can be fully utilized while being detached or connected to the automobile navigation system.